ocfs2: add locking filter debugfs file

Add locking filter debugfs file, which is used to filter lock resources
dump from locking_state debugfs file.  We use d_filter_secs field to
filter lock resources dump, the default d_filter_secs(0) value filters
nothing, otherwise, only dump the last N seconds active lock resources.
This enhancement can avoid dumping lots of old records.  The
d_filter_secs value can be changed via locking_filter file.

[akpm@linux-foundation.org: fix undefined reference to `__udivdi3']
Link: http://lkml.kernel.org/r/20190611015414.27754-2-ghe@suse.com
Signed-off-by: Gang He <ghe@suse.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>	[build-tested]
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/dlmglue.c

@@ -2991,6 +2991,8 @@ struct ocfs2_dlm_debug *ocfs2_new_dlm_debug(void)
 	kref_init(&dlm_debug->d_refcnt);
 	INIT_LIST_HEAD(&dlm_debug->d_lockres_tracking);
 	dlm_debug->d_locking_state = NULL;
+	dlm_debug->d_locking_filter = NULL;
+	dlm_debug->d_filter_secs = 0;
 out:
 	return dlm_debug;
 }
@@ -3090,10 +3092,34 @@ static int ocfs2_dlm_seq_show(struct seq_file *m, void *v)
 	int i;
 	char *lvb;
 	struct ocfs2_lock_res *lockres = v;
+#ifdef CONFIG_OCFS2_FS_STATS
+	u64 now, last;
+	struct ocfs2_dlm_debug *dlm_debug =
+			((struct ocfs2_dlm_seq_priv *)m->private)->p_dlm_debug;
+#endif
 
 	if (!lockres)
 		return -EINVAL;
 
+#ifdef CONFIG_OCFS2_FS_STATS
+	if (dlm_debug->d_filter_secs) {
+		now = ktime_to_us(ktime_get_real());
+		if (lockres->l_lock_prmode.ls_last >
+		    lockres->l_lock_exmode.ls_last)
+			last = lockres->l_lock_prmode.ls_last;
+		else
+			last = lockres->l_lock_exmode.ls_last;
+		/*
+		 * Use d_filter_secs field to filter lock resources dump,
+		 * the default d_filter_secs(0) value filters nothing,
+		 * otherwise, only dump the last N seconds active lock
+		 * resources.
+		 */
+		if (div_u64(now - last, 1000000) > dlm_debug->d_filter_secs)
+			return 0;
+	}
+#endif
+
 	seq_printf(m, "0x%x\t", OCFS2_DLM_DEBUG_STR_VERSION);
 
 	if (lockres->l_type == OCFS2_LOCK_TYPE_DENTRY)
@@ -3243,6 +3269,17 @@ static int ocfs2_dlm_init_debug(struct ocfs2_super *osb)
 		goto out;
 	}
 
+	dlm_debug->d_locking_filter = debugfs_create_u32("locking_filter",
+						0600,
+						osb->osb_debug_root,
+						&dlm_debug->d_filter_secs);
+	if (!dlm_debug->d_locking_filter) {
+		ret = -EINVAL;
+		mlog(ML_ERROR,
+		     "Unable to create locking filter debugfs file.\n");
+		goto out;
+	}
+
 	ocfs2_get_dlm_debug(dlm_debug);
 out:
 	return ret;
@@ -3254,6 +3291,7 @@ static void ocfs2_dlm_shutdown_debug(struct ocfs2_super *osb)
 
 	if (dlm_debug) {
 		debugfs_remove(dlm_debug->d_locking_state);
+		debugfs_remove(dlm_debug->d_locking_filter);
 		ocfs2_put_dlm_debug(dlm_debug);
 	}
 }

fs/ocfs2/ocfs2.h

@@ -223,6 +223,8 @@ struct ocfs2_orphan_scan {
 struct ocfs2_dlm_debug {
 	struct kref d_refcnt;
 	struct dentry *d_locking_state;
+	struct dentry *d_locking_filter;
+	u32 d_filter_secs;
 	struct list_head d_lockres_tracking;
 };